Please under I am speaking from my experiences and what I've been taught not from any official source. Your questions can be answered in detail through some reading on the web or in books written.
Previous knowledge - Navajo, Hopi and most Pueblo cultures living in the Southwest talk of past existence. The Hopi emerged into this life through the reeds found where the Colorado and Little Colorado River confluence in the Grand Canyon (pictures of that place can be found on the web...amazing). So this is not the first life for them. Before this period they lived underground. The Navajo tell a similar story where a bird busted through the ground to give them light and they emerged out of the ground. But the key is they were alive under the ground. Ironically the Grand Canyon and the landscape around the mountains of the Colorado Plateau are filled with a massive cave system. So big that geologists have no clue how big the system really is. So it could be scientifically possible that their creation story could be true the cave system and underground water in the area is big enough that human life could survive.
Here is a starting point via the web....
"The Hopi, Zuñi, Keres, and Jemez Pueblo people account for their origins by emergence from underground (Kirchhoff 1954; see Pueblo Texts), The Tanoan-speaking Pueblos (except Jemez) believe in emergence from underwater. The Navajo believe in emergence from underground fleeing rising water (Zolbrod 1984; see Navajo Texts), and the Jicarilla Apache believe in emergence from underground in pursuit of light (Russell 1898; Goddard 1911; see Apache Texts).
In their cosmogonic* accounts, these people recognize that living creatures are born. Our progenitors are gendered and increase occurs through reproduction (Farella 1984). The Pueblo accounts note that the people were created here, in place, in the Southwest. The Navajo accounts have some people created in the Southwest and some created in California and migrating east to Dinétah (Matthews 1883, Stephen 1930, Goddard 1933, Wheelwright 1942 Fishler 1953, O'Bryan 1956)."
http://drarchaeology.com/culthist/origins.htmI don't know if they had previous experience (the Navajo) with uranium. I see it as their Creator gave them instructions of what to do in this lifetime (life on upper surface of the planet).
Also I note, since this isn't the first time Tribal citizens have lived, they then deal with the end. For Hopi they believe they are in the Fourth Cycle (the fourth cycle of their life) and about to enter the Fifth Cycle. Every other shift or change has occurred with no negative impact. But this time they are longer certain how things will go. The Hopi see their prophecies coming true as do the Navajo elders. It is too much to type here. I'd suggest reading Hotevilla - Hopi Shrine of the Covenant, Microcosm of the World. This book was written as the request of the Tribal Elders who live in the village of Hotevilla, Third Mesa. The book is essentially the Hopi story told by the elders. It is a pleas to all to wake up and stop the destruction.
Hope this helps some.